//匿名函数自调用
;(function(window,undefined){
    function init(el){
        let els = document.querySelectorAll(el)
        for(let i=0;i<els.length;i++){
            this[i] = els[i]
        }
        this.length = els.length
        // let arr=[]
        // arr.push.apply(this.els)
    }
    let jQuery = function(el){
       return new init(el)
    }
    jQuery.extend = function(object){
        for(let key in object){
            init.prototype[key] = object[key]
        }
    }
    init.prototype = {
        css(cssAttr,cssVal){
            // console.log(this);
            for(let i=0;i<this.length;i++){
                this[i].style.cssAttr = cssVal
            }
            return this
        },
    }
    window.jQuery = window.$ = jQuery
})(window)